This invention relates to improved packages and more particularly, to packages which can be sterilized by conventional means after sealing, which are capable of maintaining the sterility of the contents, which can be readily opened and which provide for the controlled removal of the contents by a sterile technique.
Surgical articles and the like have been packaged and then sterilized in order to reduce the hazard of cross-infection in hospitals. Many of the packages previously employed have, however, been found to have serious disadvantages. Some of these, for example, have been difficult to open, requiring tearing or cutting and, hence, exposing the article, when withdrawn, to contamination by the non-sterile, exterior, torn or cut edges of the package. Other prior packages have suffered from the disadvantage of not permitting positive control of the sterile contents while opening the package to prevent the contents from dropping out and being contaminated. Another disadvantage of some prior packages is that they have been found to have unsealed channels through the seal lines closing the package at points where more than two sheets of packaging material are joined. Packages of this type tend to breathe, particularly when stored under conditions where there is a wide variation in temperature or atmospheric pressure. This is highly disadvantageous since it makes possible the introduction of airborne bacteria which may contaminate the contents of the package and cause the loss of sterility.
U.S. Pat. No. 3,070,225, issued on Dec. 25, 1962 to M. A. Schwartz and U.S. Pat. No. 3,324,705, issued on Feb. 15, 1966, also to M. A. Schwartz, disclose packaging for sterile articles and, in particular, disclose that the channel problem, referred to above, may be solved by providing a thermoplastic "calking" adhesive to flow into and block such potential channels. The concept disclosed is to provide a package comprising a top and bottom sheet. The bottom sheet has a peripheral portion or side edge of each of its longitudinal sides folded inwardly to overlie the bottom sheet and form longitudinally extending side flanges. The article packaged may then be partially held under the flanges in a controlled and positive manner. These side flanges are tacked down by applied, spaced areas of adhesive. A top sheet is then laid over the bottom sheet with the article and the side flanges therebetween. The top sheet is sealed to the bottom sheet by longutidinal side seals in the area where the top sheet overlies the side flanges and by transverse end seals spanning the two side flanges. The problem of channeling toward which the Schwartz patents are directed occurs at the end seals where the seal passes first through at least three thickness of packaging material (corresponding to the bottom sheet, the flange at one side and the top sheet), then two thickness (corresponding to the top sheet and the bottom sheet) and then again three thickness (corresponding to the bottom sheet, the flange at the other side, and the top sheet). It is at the point where the seal crosses from three to two thickness of packaging material, that the channeling problem exists. The solution suggested in the aforementioned Schwartz patents is to provide, for the spaced adhesive areas used on the bottom sheet for tacking down the flanges, a thermoplastic adhesive which is applied to the bottom sheet so as to extend beyond the area of contact between the flange and the bottom sheet. In this manner, when heat and pressure are applied to produce the end seal, at the same time the thermoplastic adhesive will be activated and become flowable, thus acting as a calk to block the potential channels.
This solution has been highly satisfactory and is particularly effective when both the top sheet and the bottom sheet are provided with the same, or otherwise adhesively compatible, adhesives. By the term "adhesively compatible adhesives" it is meant two adhesives which, upon activation, will seal together at their interface. Unfortunately, it is not always possible or desirable to provide the top and bottom sheets with adhesively compatible adhesives. In the circumstance where the adhesive applied to the top sheet for side and end sealing is adhesively incompatible with the adhesive used on the bottom sheet to tack down the flanges, the solution offered by the aforementioned Schwartz patents is not only inappropriate, but actually aggravates the problem. In this case, the calking adhesive does flow, upon end sealing. Instead of creating a seal, however, a relatively long interface of noncompatible top and bottom sheet adhesive is created at portions of the end seal between and adjacent to each flange. Accordingly, because of the incompatibility of the adhesives, this long interface is, in effect, a channel into the interior of the package, rendering the same entirely unsuitable for sterile articles.
It is apparent, therefore, that the need exists for a package for sterile articles which does not suffer from these drawbacks.